Nuthin could be easier.

In the serverless.yml set the triggering event from schedule.

...
functions:
  ...
  my-scheduled-code:
    description: Some test for scheduled run
    handler: src/functions/myScheduled.handle
    events:
      - schedule: rate(1 minute)
...

As for schedule parameter there is two function cron and rate.

Links:
https://serverless.com/framework/docs/providers/aws/events/schedule/
https://docs.aws.amazon.com/lambda/latest/dg/tutorial-scheduled-events-schedule-expressions.html